textproduct: Albany

WHAT HAS CHANGED

The latest operational model runs and ensembles have been coming in with higher snowfall totals for Thursday night into Friday, mainly for high terrain areas. Have continued to adjust forecast based on the latest guidance and NBM, although there still remains a large degree of forecast uncertainty regarding exact p-type and boundary layer temps, especially in valley areas.

KEY MESSAGES

1) An early season accumulation of snow is likely across northern and high terrain areas for Thursday into Friday thanks to a storm system passing to the south. However, there remains a large amount of uncertainty regarding if rain will change over to snow and accumulate in valley areas.

DISCUSSION

KEY MESSAGE 1...

A storm system is expected to track across the Midwest and Ohio Valley on Wednesday into Wednesday night. By Thursday, the low pressure area looks to track just south of the area across the northern mid Atlantic before passing close to the coast of Long Island and southern New England for Thursday night. As a large upper level trough approaches from the west, this low pressure area will slowly sit and spin close to the coast of eastern New England on Friday before exiting into the western Atlantic Ocean by Friday night. There still remains some uncertainty regarding just how quick the storm exits for Thursday night into Friday, as it will depend on the interaction with the approaching upper level low.

A period of warm advection will lead to the initial light precipitation for Wednesday night into early Thursday. This looks to be rain to start across the entire region. However, the combination of wet-bulbing and dynamic cooling will allow for precipitation to change over to snow across the high terrain of the Adirondacks during the day on Thursday. Cooling temps aloft thanks to the approaching upper level trough will allow for more of the higher terrain of the region to see a change over to snow for Thursday night into Friday. Some models suggests that some banding precipitation within the deformation could even allow for precip in valley areas to switch over to snow as well by Friday morning, although this will depend on the exact track and strength of the storm system and if enough cold air can arrive in time. Heavier bands of precip could help allow for dynamic cooling to flip p-type over to snow as well. Steady light precip looks to occur during the day on Friday as an inverted trough sets up. Eventually, precip will tend to taper to mainly snow showers and flurries by late Friday into Friday night, as the surface low departs and the upper level trough moves overhead.

Model guidance has been showing varying solutions lately, but much of the guidance has been hinting at this potential for more wintry precip over the past few runs. Some runs of the RRFS have shown a light to moderate accumulation in valley areas, with moderate to heavy accumulation across the high terrain. With these models being rather new and this being a unique early season event, there is somewhat limited confidence in how this newer guidance will handle this system. In addition, there has been vastly different solutions with each run, which also limits confidence.

The WPC WSO from earlier this evening been fairly low (10-30%), although it may start to jump up with the newer guidance. We have been leaning towards the probabilistic WSSI from WPC which suggests a 30-50% chance of minor impacts across the high terrain at this time. As newer guidance arrives, there numbers are likely to change, so this is a rather fluid situation. The NBM probabilities are just starting to rise, so will continue to closely monitor those numbers as well. For now, the Adirondacks look to be the most-favored and at least an advisory will probably be needed there and perhaps across southern VT as well. Elsewhere, it's a big question mark on how much, if any, snow will actually accumulate. This will likely come into better focus over the next day or so.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Through 12Z Thursday...VFR conditions are expected to prevail prior to 06Z/Thu for KGFL/KALB/KPOU/KPSF. A few-sct post frontal stratocumulus will persist this morning with potentially sct-bkn clouds at KGFL. Mid and high clouds will quickly increase from the south and west during the afternoon. Most of the TAF sites should have a broken to overcast mid level cloud deck 9-12 kft AGL shortly before or just after 00Z/Thu. The clouds will further thicken and lower to 4-6 kft AGL and then some showers will arrive ahead of the warm front and wave of low pressure approaching from the Ohio Valley/PA between 08Z-12Z/Thu. Flight conditions will lower to MVFR cigs/vsbys.

The winds will continue from the west to northwest around 10 KT during the late morning into the afternoon before becoming light and variable at 4 KT or less to calm by around 00Z/Thu. KPSF may have a few wind gusts 15-20 KT prior 17Z/Wed. The winds will be north/northeast at 5 KT or less after 06Z/Thu.

Outlook...

Wednesday Night: High Operational Impact. Definite RA...SN. Thursday: High Operational Impact. Definite RA...SN. Thursday Night: Moderate Operational Impact. Chance of RA...SN. Friday: Moderate Operational Impact. Chance of RA...SN. Friday Night to Sunday: No Operational Impact. NO SIG WX.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.